Agitating retorts are widely used for in-container preservation of foodstuffs, either for pasteurization or sterilization processes. FIGS. 1-3 illustrate constructions of known agitating retorts. Referring initially to FIGS. 1 and 2, the illustrated agitating retort 18 consists of an outer retort shell 20, which in essence is a generally cylindrically shaped pressure vessel that houses a drum 22 for rotation within the shell. The drum is adapted to receive baskets 24 within which are stacked containers of foodstuffs or other products to be processed. The containers may be in the form of cans, glass jars, or of other types. Alternatively, the foodstuff containers may be arranged on trays carried by pallets, not shown. The baskets of foodstuff containers are held in place within the drum to restrain the baskets and containers during the retorting process.
The drum 22 may be of various constructions, including that shown in FIGS. 1 and 2, wherein the drum is shown as being of an open design. Drum 22 is constructed from a number of spaced-apart vertical discs 30 that are joined together by a series of longitudinal tube structures 32 spaced about the perimeter portion of the discs to provide structural strength of the drum. Reinforcing braces 34 may be welded or otherwise affixed between the tubes in a crisscross pattern for further structural strength and/or rigidity. A door 36 is used to close the open end of the shell 20 into which baskets holding the containers are loaded and unloaded from the drum 22.
In some retort processes the drum 22 is rotated about its longitudinal axis. Rollers 38 located in the lower portion of retort shell 22 support the drum for such rotation of movement. A powered shaft 40 may be coupled to the end of the drum opposite door 36 for rotation of the drum. As shown in FIG. 2, generally square- or rectangular-shaped openings 42 are formed in the discs for receiving the baskets 24. Various types of clamping systems, not shown, may be used to hold the containers and baskets in place when the drum is rotated
The retorting process may be of various types, including water spray, combined water and steam spray, and water immersion. In the water spray and combined water and steam spray process, the processing fluid is typically supplied to an inlet 48 at the top portion of the retort, and then through lines or pipes 50 running the full length of a retort shell in the space between the inside diameter of the shell and the outside diameter of the drum. Injection holes or nozzles 52 are disposed along the length of the pipes 50 for directing the processing fluid toward the containers disposed within the rotating drum. As will be appreciated, a certain portion of the processing fluid from the nozzles 52 strikes the tube structures 32 and reinforcing braces 34, and thus, may never reach the interior of the drum. Moreover, when the fluid droplets from the overhead pipes 50 actually reach the interior of the drum and contact either the drum interior, the basket or containers, such droplets are during rotation of the drum subjected to a centrifugal force that counteracts the downward gravitational forces acting on the droplets, thereby reducing the capacity of the droplets to reach the center portion of the baskets. With increasing rotational speed of the drum this results in increasingly less uniform distribution of the processing water inside the baskets. Eventually the processing fluid collects at the bottom of the retort shell and is routed out of the shell through an outlet 54 to a recirculation pump that re-injects the processing fluid through openings in the top and sides of the retort to the lines or pipes 50.
FIG. 3 illustrates another embodiment of an existing retort which is constructed similarly to the retort shown in FIGS. 1 and 2, and thus like parts are given the same numbers, but with prime (′) designation. The retort 18′ shown in FIG. 3 is designed for use with a water immersion process. The level of processing fluid in the retort may vary, or the retort may be completely filled with the processing fluid. The processing fluid may be introduced into the retort shell by multiple inlets 48′ shown at the top of the shell 20′ over the length of the retort. Typically, one inlet 48′ is present per basket. As a consequence, the processing fluid does not flow evenly through the baskets 24, especially when the drum is held stationary. This leads to uneven heating and cooling of the containers disposed within the baskets, and thus, a variation in the sterilization value of the products in the containers. As a consequence, often it is necessary to rotate the retort drum 22′ to provide adequate mixing and distribution of the processing fluid within the retort 18′. The present invention seeks to address the limitations and drawbacks of existing retorts, including agitating retorts.